Unfortunatelly www.openhub.net doesn’t provide any way to styling widgests. Hovever i have found one way.

Here is code for the original widget
<script type='text/javascript' src='https://www.openhub.net/p/valentina-project/widgets/project_factoids_stats?format=js'></script>

As you can see the site return script by link https://www.openhub.net/p/valentina-project/widgets/project_factoids_stats?format=js

If use this link in a browser you will get
document.write("<iframe src='https://www.openhub.net/p/valentina-project/widgets/project_factoids_stats', scrolling='no', marginHeight='0', marginWidth='0', style='height: 220px; width: 370px; border: none'></iframe>");

And this code has style options. So instead of the original code we could write
<script type="text/javascript">document.write("<iframe src='https://www.openhub.net/p/valentina-project/widgets/project_factoids_stats', scrolling='no', marginHeight='0', marginWidth='0', style='height: 220px; width: 370px; border: none'></iframe>");</script>